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Eastern Hemlock

Latin name:Tsuga canadensis

Extracted from a
waterfront pier near Wilmington, Delaware, the tree used to make
this portion of the pieractually came from a forest located in
central Pennsylvania. The outermost tree ring dates to the late
1830s.

Giant Sequoia

Latin name:Sequoiadendron giganteum

A close up of numerous fire scars on a giant sequoia cross section
from Sequoia National Park in California,
dating back well prior to A.D. 1000. Look closely! Can you find the sad bearded
face cradled by his hands, as if he was crying?

Douglas-fir

Latin name:Pseudotsuga menziesii

This photo shows the tree rings from a beam extracted many years ago
from a pueblo in northeastern Arizona. The section shows many false rings
and many micro-rings, suggesting this tree may have been growing in a marginal environment.

Ponderosa Pine

Latin name:Pinus ponderosa

Close up of tree rings of a ponderosa pine collected at El Malpais National Monument in New Mexico, USA,
showing tree rings centered around A.D. 1400. Notice the variability in ring widths indicative of sensitivity to
year-to-year variation in precipitation.

Douglas-fir

Latin name:Pseudotsuga menziesii

Perhaps my most requested image of tree rings, obtained from a small
Douglas-fir growing in the Zuni Mountains of west-central New Mexico by
my colleagues Rex Adams and Chris Baisan. Not very old, but has some of the most beautiful rings of all my displays!

White Oak

Latin name:Quercus alba

Oak cores from the Hoskins House in Greensboro,
North Carolina, site of a famous battle during the Revolutionary War. The
house was built from trees cut in 1811 to 1813, not cut and built in the 1780s as the historical agency had hoped.

Ponderosa Pine

Latin name:Pinus ponderosa

This ponderosa pine once grew at El Morro National Monument in
New Mexico, USA, and was cut many years ago. Once you get up close to the stump, you can
see a very old scar from a fire many hundreds of years ago that scarred
the tree when it only about 12 years old!

Bahamian Pine

Latin name:Pinus caribaea var. bahamensis

We collected many cross sections of Bahamian pines that had been cut for
an industrial park on the island of Abaco, but the rings are very difficult to
date! Many false rings, and the pine appears to terminate tree growth during the dry season.

Longleaf Pine

Latin name:Pinus palustris

This cross section was one of many that came from an old crib dam across a creek that was exposed after a modern dam broke in Hope Mills,
North Carolina in 2003. Such sections from old-growth longleaf pines are very rare and
provide information on climate back to AD 1500!

White Oak

Latin name:Quercus alba

Sometimes you don't have to look far to find beauty in wood, and
sometimes it may not be a living tree! After an oak tree was cut a
year or two before this section was obtained, decay fungi had
already set in, beginning to break the wood down to its basic
elements.

Southwestern White Pine

Latin name:Pinus strobiformis

I collected this fire-scarred pine on Mt. Graham in southern Arizona in fall 1991,
and it remains one of the best examples of how we can determine the season of fire by looking
at the position of the scar within the ring.

Bristlecone Pine

Latin name:Pinus longaeva

Bristlecone pines have become one of the best proxy records for those who study the history of
volcanic eruptions because the cool temperatures caused by these eruptions
create "frost rings" that form when the cells implode from the cold.

Eastern Redcedar

Latin name:Juniperus virginiana

Many well-preserved eastern redcedar sections have been recovered from prehistoric sites
in eastern Tennessee, and they have more than enough rings to date, but we don't have a long enough
living-tree reference chronology to overlap with them!

Red Oak

Latin name:Quercus rubra

Oak is by far the most common genus we find in the many historic structures we date using
tree rings in the Southeastern U.S. The genus has good ring variability
and rarely has problem rings. This section came from a historic tavern in Lexington, Virginia.

Sugar Maple

Latin name:Acer saccharum

Maple, birch, beech, and basswood are all examples of hardwood species that form diffuse porous wood, meaning
that the ring contains many small-diameter vessels all through the ring. Identifying the
ring boundary on this wood type is a challenge to tree-ring scientists.

Live Oak

Latin name:Quercus virginiana

Live oak is an example of an evergreen oak, which is not common within this
genus. As such, the wood is semi-ring porous and the rings are very
difficult to see and date. Ring growth is also very erratic, not forming the concentric around the tree that we require.

Douglas-fir

Latin name:Pseudotsuga menziesii

These cores were collected on Mt. Graham in southern Arizona and
show a major suppression event beginning in 1685 when missing rings
became evident, followed by many micro-rings. This suppression was
caused by a major wildfire in 1685!

Ponderosa Pine

Latin name:Pinus ponderosa

I find it amazing what trees can record in their tree rings! Here we see a cross section of a pine
that was damaged by a major flood in the year 1945 in the Chiricahua Mountains of
southern Arizona. Notice the reaction wood that formed afterward.

Subalpine Fir

Latin name:Abies lasiocarpa

Decay has set in on the tree rings of this dead and downed subalpine fir that once grew on Apex Mountain
in British Columbia, Canada, but the tree rings can still be measured and crossdated despite this!

White Fir

Latin name:Abies concolor

We found a beautiful fire scar on this white fir that was used to build a cabin in the Valles Caldera of New Mexico.
Thought to have been built in the early 1900s, we instead found the cabin was built form white fir and Douglas-fir trees cut in 1941.

Overcup Oak

Latin name:Quercus lyrata

These oak cores were collected in northeastern Arkansas to investigate a change in the hydrologic regime of a
wildlife refuge beginning in the 1990s. We found that trees at this site experienced a major disturbance event in the 1960s.

Western Juniper

Latin name:Juniperus occidentalis

Near Frederick Butte in central Oregon, we discovered an unusual stand of western junipers that had the most
unusual lobate growth forms we had ever seen. This site yielded a drought-sensitive chronology dating back to the AD 800s!

West Indies Pine

Latin name:Pinus occidentalis

Above 3000 meters on the highest peak in the Carribean, we found an entire forest of these pines, many with fire scars, living
on a steep rocky slope. The forest looked more like the dry ponderosa pine forests of the western U.S.

Whitebark Pine

Latin name:Pinus albicaulis

Whitebark pines growing in the northern Rockies of the western U.S. can grow to be over 1,000 years old, but the
species is slowly being decimated by the introduced white pine blister rust. Many of these ancient trees are now dead with
ghostly white trunks.

Shagbark Hickory

Latin name:Carya ovata

Curiously, tree-ring scientists rarely analyze some of the more common hardwood species in the eastern U.S., such as this hickory, perhaps because
such forest interior trees may contain a weak climate signal necessary for crossdating.

Virginia Pine

Latin name:Pinus virginiana

Blue stain found in many sections of dead pines (both in the western and eastern U.S.) is caused by a fungus carried by a
pine beetle. The fungus spreads into the phloem and sapwood of living and dead pines, sometimes
creating stunning patterns!

Pinyon Pine

Latin name:Pinus edulis

Burned sections of pinyon pine are commonly found in archaeological sites in the southwestern U.S. These sections can be carefully
broken or surfaced with a razor to reveal the ring structure inside to assist in dating the years of construction of the site.

Red Spruce

Latin name:Picea rubens

Conifers in the highest elevations of the Appalachians of the eastern U.S., such as this red spruce, don't experience wildfires very
often, but when fires do occur, they can create numerous fire scars even in this fire-intolerant species. Notice the growth release!

White Spruce

Latin name:Picea glauca

This tree was located in the Canadian Rockies on the toe slope of an active avalanche path. The scar was created by a debris
flow or snow avalanche which struck the tree, killing a section of the living tissue. The avalanche can therefore be dated to its exact year!

Engelmann Spruce

Latin name:Picea engelmannii

I worked considerably in the spruce-fir forests of southern Arizona in my earliest years in dendrochronology, and
learned that trees with limited sensitivity can provide a vast amount of information on the history of these forests.

Ponderosa Pine

Latin name:Pinus ponderosa

The lava flows of El Malpais National Monument in New Mexico contain vast amounts of remnant wood, mostly ponderosa pines such as this sample,
and the tree rings on these samples go back nearly 2000 years! Notice the year AD 1400 on this section.

Chestnut Oak

Latin name:Quercus montana

In the southeastern U.S., hardwood species are often scarred by wildfire. Most often, this also will cause considerable
decay in the sample, but this oak had several well preserved fire scars, suggesting fire was common in these drier, lower elevation sites.

Ponderosa Pine

Latin name:Pinus ponderosa

I originally sampled this stump in 1991 for its fire scars, located in El Malpais National Monument of New Mexico. I found it again 20 years later
and was happy you could still see the tree rings and fire scars clearly! It had originally been logged in the 1930s!

Lodgepole Pine

Latin name:Pinus contorta

This pine is found at higher elevations in the Rocky Mountains of the western U.S. At this site in Montana, we had thought we found fire scars on
these pines, but it turns out that these are scars caused by bark beetles stripping away portions of the bark.

Douglas-fir

Latin name:Pseudotsuga menziesii

These cores illustrate the level of sensitivity to climate fluctuations in Douglas-fir trees growing in El Malpais National Monument in New Mexico.
These rings show the common pattern of narrow marker rings between 1800 (on the left) and 1860 (on the right).

Douglas-fir

Latin name:Pseudotsuga menziesii

This photo shows a close-up of the rings in the previous image. The very wide tree ring is the year 1816, the "Year
Without a Summer." Cooler temperatures meant more soil water for the malpais Douglas-firs, causing a wide ring for that year!

Ponderosa Pine

Latin name:Pinus ponderosa

Dating fire scars found in the annual rings is a major application of tree-ring dating. This photo shows two scars. Notice
the wider rings that formed after the upper scar, perhaps caused by removal of competing vegetation or added nutrients.

Longleaf Pine

Latin name:Pinus palustris

Longleaf pines have the greatest ages of all the eastern pines. They grow slowly in sandy soils of the Atlantic Coastal Plain, and have
proven ideal for learning about past climate and disturbance events, if old-growth stands can be located!

Rocky Mountain Juniper

Latin name:Juniperus scopulorum

The juniper species of the western U.S. have proven a challenge in tree-ring dating, but Rocky Mountain juniper has tree rings that
are easily identified and can be crossdated. Just watch out for false rings and expanded latewood!

Douglas-fir

Latin name:Pseudotsuga menziesii

A close-up photo of tree rings in Douglas-fir reveals the individual wood cells that make up the xylem. These are called "tracheids."
Notice the change in cell wall thickness from the earlywood cells to the latewood cells along a radial file of cells.

Douglas-fir

Latin name:Pseudotsuga menziesii

The best trees for learning about past climate will be those that grow to great ages and are particularly sensitive to year to year
changes in climate. This Douglas-fir began growing around the year 200 BC and lived for nearly 1000 years!

Mesquite

Latin name:Prosopis glandulosa

Some desert species from the mid-latitudes do form annual rings, but these diffuse-porous species have rings that are difficult to
see. You can use black marker and white chalk dust to help bring out the rings! The dust fills the small vessels and the rings appear!

Norway Spruce

Latin name:Picea abies

Spruce is the preferred genus for making high-quality wooden bodies on musical instruments. This photo shows the tree rings on the outer
edge of the "Messiah" violin. Analysis of its tree rings helped show that the violin was contemporary with Stradivari!

Black Locust

Latin name:Robinia pseudoacacia

In the eastern U.S., this common hardwood species has beautiful tree rings that demonstrate the ring porous wood type. The tree species,
however, has some of the densest wood found in North America and is extremely difficult to core!

White Oak

Latin name:Quercus alba

Oak is a major genus used to build log structures in the eastern U.S. Sometimes, however, we find that the individual trees experienced some
major disturbances that caused very aberrant rings, making crossdating all but impossible.

Palo Verde

Latin name:Parkinsonia florida

A common tree species in the American Southwest, palo verde is a diffuse porous species that forms very indistinct tree rings.
As a result, little tree-ring research has been performed on this genus. Best to use complete cross sections, when available.

Ponderosa Pine

Latin name:Pinus ponderosa

A major application of tree-ring research is learning about insect populations. For example, pandora moth defoliated the needles on this tree,
causing some narrow rings to be produced. We can use this pattern to learn about insect populations over many centuries!

Table Mountain Pine

Latin name:Pinus pungens

The analysis of fire scars in tree rings can also be applied to pine species growing in the eastern U.S. Table Mountain pine has proven
to be the best species in the Appalachian Mountains for learning about past wildfires!

Subalpine Fir

Latin name:Abies lasiocarpa

Subalpine fir grows in the highest elevations of the southern Rocky Mountains and forms fairly compacent ring series. Sometime between
1979 and 1980, this tree was stripped almost completely of its bark by a black bear, but it still survived in one small area!

Florida Torreya

Latin name:Torreya taxifolia

Perhaps the rarest conifer in the U.S., this species is on the brink of extinction because its habitat is facing mounting pressure
from rapid changes in its native environment. It forms very nice tree rings, but few adult individuals are left to analyze.

Featured...

The 26th European
Dendroecological Fieldweek will be held from 30 August–6 September
2015 in Zawoja, Poland, with accommodations provided by the Lajkonik Hotel.
Topics will cover the full spectrum of dendrochronological issues and foster
cross-disciplinary links.

What I do...

The Science of Tree Rings web site is a not-for-profit educational and informational site
designed to be used by people of all ages, from elementary school students and teachers to
university students to seasoned professionals and academics at all levels of
education.

Who I am...

I've been involved in dendrochronology since 1985
and started this web site back in 1994. I teach and conduct research at the
University of Tennessee where I'm a Full Professor in the Department of
Geography and direct the Laboratory of Tree-Ring Science.

Archaeological Tools

Special drill bits and tools are needed if you will
be extracting cores from archaeological samples where
the wood (usually hardwood) is very dry. Regular increment
borers are insufficient and often unable to extract sound
cores from such samples. Instead, dendroarchaeologists use a
specially designed hollow drill bit driven by a
heavy-duty industrial-style drill.

This is the company I use
to create my custom-designed drill bits. The package comes
as a three-piece kit that includes the 10" long drill bit, a polyethylene guide
plate, and a sharp, curved extractor to dislodge the core
from inside the wood beam. The cost for the 3-piece dry wood
borer kit is $US 159.95.
If you'd like to learn more about how to use of a dry wood
borer, be sure to read my
tutorial
for properly and safely using the drill bits. The drill I prefer is a DeWalt DW245 7.8 amp 0.5 inch
variable speed drill ($140.00) and you can order this from
my online tree-ring supply store. I will say
that I've used battery-powered (cordless) drills in the past
also, but prefer to use corded drills for a continuous power
supply and a lighter drill.

Extracting good samples from
dry wood is a delicate job. A good tool is the prerequisite
for every researcher investigating construction timber.
RINNTECH offers dry wood borers with 8/16 mm diameter. They
were developed by Thomas Bartholin and slightly improved by
RINNTECH. RINNTECH dry wood borers can be run with
commercial electric drills (600 W power). They are available
in lengths of 150 mm, 250 mm and 350 mm. Application is
possible in softwoods as well as in hardwoods. A maintenance
set allows cleaning and sharpening of the borers.

The borers were developed in
cooperation with the dendro laboratory of the Deutsches
Archäologisches Institut Berlin (the German Archaeological
Institute, Dr. Karl-Uwe Heußner DAI, Ref. Naturwiss, Im Dol
2-6, Haus IV,D-14195 Berlin) to be able to carry out
samplings with minimal side effects. They are suitable for
dendrochronological examinations especially at historical
construction timber and are conceived for the use in solid
dry wood. Fresh wood can be bored more or less well
depending on its nature. Boring into wet wood causes
problems with the chip removal. Moreover, the wood core can
become wedged in the borer by the swollen condition.

More information

Rob Wilson adds this
information: "I used three dry archaeological corers in
Germany which cost me about $US 20-30. They were home made.
One can buy cutting bits (with teeth etc) at most home
hardware stores. I used two sizes, 14 mm and 21 mm. The
length of these bits varied from 2 cm for the wider to 3.5
cm for the thinner. Luckily I had a friend who worked in a
machine shop, who welded the bit onto a tube of same
diameter and thickness. This is the tricky bit, because the
join must be flush and smooth (inside and out).

"The
opposite end...i.e. the end that goes into the drill is also
problematic. The Tucson system has a separate attachment
that the corer twists into. Mine was a one piece system.
Again a thick walled hollow piece of metal (but smaller
diameter) was welded onto the end. The diameter of this can
vary, but this depends on what diameter bits your drill can
take. This piece must have a whole through it, because you
will quite often want to push the wood sample out of the
corer.

"A little refinement on the
Tucson system was an idea that I picked up from the
archaeological lab in Sheffield. At periodic intervals down
the bit, holes should be drilled through the walls of the
corer (ca. 5 mm). Mine were drilled in a pseudo spiral
pattern of about 7 cm distance apart. Because one is coring
dry wood, there is a lot of dust that can clog the corer and
sample when drilling. A lot of dust will come out of these
holes. Be sure to smooth the burr created when making theses
holes.

"The problem still remains on
how to get the sample from the beam. Quite often once you
have drilled your 30 cm into the beam, the sample will still
be attached to the beam (though it can sometimes come out in
the corer). You need an extractor. Bicycle spokes are good
for this. You want to bend one into a L shape with the
longest end being the same length of your corer. At the end
of this, with some sharp pliers, you want to 'pinch' a sharp
point at right angles. When taking the sample out, there
will be a gap around the sample and the beam. Enter the
extractor along this gap as far into the beam as possible.
When you reach the end, twist the extractor so the sharp
point will attach itself to the bottom end of the sample and
pull. The sample should come right out in one piece."

Geoff Downes adds: "CSIRO
developed a corer for a powered drill bit which should do
the job. It extracts a 12 mm core and leaves a 22 mm hole.
This is a standard dowel size for plugging. It comes in two
lengths, 300 mm and 500 mm. I have used the corer myself and
it does a good job. The only drawback is the need to return
it to the suppliers for re-sharpening. They are yet to
supply a sharpening jig for others to do it." Contact CSIRO
at: CSIRO Forestry and Forest Products, GPO BOX 252-12,
Hobart, 7001, Tasmania, AUSTRALIA.

Olafur Eggertsson writes: "You
should contact Thomas Bartholin in Copenhagen - he has the
best corers, with prices from c. 4000.- DKR."

Permissions

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used freely for non-profit educational purposes only and only after securing
permission from me. Small charges apply for use of certain graphics and images
by commercial for-profit companies. Please contact me for details. If you use any material or information from
these copyrighted web pages when making your own, I expect an acknowledgment.